The present invention relates to a communication system for performing data communication between one master unit and a plurality of slaves, for example, in an office or at home, and it relates to a communication device and a communication method for use in this communication system.
In a wireless network formed by a plurality of wireless communication terminals, by setting one master and a plurality of slaves, mutual wireless data communication can be established between the master and the respective slaves. For example, the Japanese Patent Publication Laid-Open No. 4-241533 describes that a wireless network is established between one master and a plurality of slaves, so to perform time division multiplexing communication between each terminal.
Considering the case of data communication between one master and a plurality of slaves, from the viewpoint of a slave, communication between the master and itself means one-to-one communication and the slave is only to sent and receive data at the time slot of its own. The master, however, must send and receive data to and from all the slaves. Therefore, it takes much more time to send and receive the data compared with the slave. In this case, relationship between a master and slaves is fixed in the conventional system, and it is impossible to change the relationship. Therefore, a role of a master is always concentrated on one, and the power consumption of this terminal becomes greater than any other terminal (slave).
As mentioned above, in the case of data communication between one master and a plurality of slaves, communication load is extremely increased in a terminal established as a master. Therefore, in the case of activating each terminal on battery, battery is exhausted soon in a terminal established as a master, and this terminal must leave the wireless network because of the battery exhaustion.
More specifically, assuming that, for example, in a conference hall, each participator carries his or her portable personal computer provided with a wireless communication function, and that, with a personal computer of a participator regarded as a master and the personal computers of the other participators regarded as slaves, the master computer receives data from each slave computer and sends the received data to each slave computer, communication concentrates on the personal computer first established as a master. Therefore, the battery of this computer goes dead in a shorter time than that of any other slave computer of the other participators, thereby causing a problem that the participator of this computer cannot take part in the conference thereafter.